PYRAZOPHOS RESIDUES FROM TREATED GREENHOUSE AND GROWTH CHAMBER GROWN CHRYSANTHEMUMS

Abstract

Potted and cut flower chrysanthemums (Chrysanthemum morifolium Ramat) were sprayed with 450 mg L−1 a.i. of pyrazophos grown under growth chamber and greenhouse conditions, respectively. A multiresidue method was tested for use on extraction and determination of pyrazophos on chrysanthemums and it was found to give 96% recoveries. Under growth chamber conditions pyrazophos disappeared from potted chrysanthemum plants with a half-life of between 19 and 25 d. On day 0, after allowing the spray to dry, 82% of the residue was removed by washing; at day 35, the amount removed was 43%. Removal by swabbing over the 35 d varied from 4.2% to 7.1%. In six commercial cut flower crops of greenhouse grown chrysanthemums, no evidence of pyrazophos breakdown was observed in plant tissues analyzed between the last spray date and sale of flowers 14 d later. During this period, swabs (wipings) dislodged between 2.7 and 4.6% of surface pyrazophos residue. These data strongly support a recommendation to wear gloves when handling both cut and potted chrysanthemums as workers can spend 30 and 60 h, respectively, handling the crop over each 13- to 15-wk production period.Key words: Pyrazophos, residues, chrysanthemums, greenhouse